I'm fairly sure Fraps is safe. I've heard a lot of people talk about using it for benchmarking and capture, and haven't heard any complaints. As far as pay vs. free, I'd say start with the free version, see how it works for you, then consider upgrading if it doesn't fit your needs with just the free version. I know that the free version locks some features, like I think it limits the FPS at which you can capture video, as well as putting a "captured by Fraps" watermark on your video if you use the free version.